The invention relates to a wind energy installation and to a wind farm which consists of these wind energy installations.
Electrical energy which is produced using wind as the stochastic primary energy source by means of wind energy installations in a wind farm is intended to be fed into a regional supply grid.
One known concept for a wind farm 2 is illustrated schematically in FIG. 1 of DE 196 20 906 A1. This known concept is a decentralized polyphase concept, because the energy from each wind energy installation 4 in the wind farm 2 is fed into a regional supply grid 6. Since the increase in the voltage at a wind farm feed point 8 of the regional supply grid 6 must not be more than 4%, this results in a maximum possible wind power, depending on the distance between the wind farm feed point 8 and a substation for this supply grid 6. The illustrated wind farm 2 has three wind energy installations 4, which each have a pod 12 and a tower 14. The pod 12 is arranged on the tower 14 such that it can rotate and has a generator 16, a generator-side filter 18, a generator-side converter 20, a grid-side converter 22, a grid-side filter 24 and a transformer 26. The two converters 20 and 22 are electrically conductively connected to one another on the DC voltage side by means of a DC-link circuit. These two converters 20 and 22 and the DC-link circuit therefore form a DC-link converter.
One design of a DC-link converter such as this arranged in a pod 12 of a wind energy installation 4 is disclosed in the publication entitled “A high power density converter system for the Gamesa G10×4.5 MW Wind turbine” by Björn Andresen and Jens Birk, published in the Proceedings of EPE 2007 in Aalborg. In this DC-link converter, which is described in this publication, the two converters 20 and 22 are in the form of self-commutated pulse-controlled converters. In order to make it possible to keep harmonics produced by the converters 20 and 22, respectively, away from the generator 16 and the supply grid 6, respectively, respective filters 18 and 24 are provided on the generator side and on the grid side. A converter output voltage which is generated is matched to a rated voltage of the regional supply grid by means of the grid-side transformer 26.
As can be seen from the cited publication, the generator 16 is linked directly or by means of a gearbox on the rotor side to a rotor of the wind energy installation 4. If a synchronous generator is used as the generator 16, there is no need for the gearbox, thus reducing the weight of the pod 12. The rotors are not illustrated in this FIG. 1, for clarity reasons.
FIG. 2 shows a second embodiment of the polyphase concept of a wind farm 2. This embodiment differs from the embodiment shown in FIG. 1 in that the electrical equipment in a wind energy installation 4 is no longer arranged in the pod 12 but in the tower 14. An embodiment such as this of a wind energy installation 4 is disclosed in the publication entitled “ABB Advanced Power Electronics—MV full power wind converter for Multibrid M5000 turbine”, published on the Internet, on the site www.abb.com/powerelectronics. The installation parts 18, 20, 22, 24 and 26 are arranged in the foot area of the tower 14 of a wind energy installation 4. Only the generator 16 therefore still remains in the pod 12 of each wind energy installation 4 in a wind farm 2.
DE 196 20 906 A1 discloses a wind farm 2 having n wind energy installations 4. In this known wind farm 2, each wind energy installation 4 has a rotor 28, whose rotor blades are variable, a synchronous generator 30, a rectifier 32 and a smoothing inductor 34. The synchronous generator 30 is coupled directly to the rotor 28 and has two stator windings, which are electrically offset through 30° with respect to one another and are each electrically conductively connected to a partial rectifier 36 of the rectifier 32. The synchronous generator 30 may have permanent-magnet excitation or voltage-regulated excitation. The rectifier 32 is a multi-pulse design, for example a 12-pulse design. By way of example, the smoothing inductor 34 is arranged in a positive output line 38. This positive output line 38 and a negative output line 40 can respectively be disconnected from a positive and negative busbar 44 and 46 by means of a circuit breaker 42. The n wind energy installations in the wind farm 2 are connected in parallel on the direct-current side by means of these two busbars 44 and 46.
A grid-side converter station 48 in this illustration of a direct-current concept of the wind farm 2 is arranged directly adjacent to a substation 50 of a regional supply grid 6. This grid-side converter station 48 has a smoothing inductor 52, an inverter 54, a matching transformer 56 and a filter 58. In the same way as the rectifier 32 in each wind energy installation 4, the inverter 54 consists of two partial inverters 60. The number of pulses in the inverter 54 corresponds to the number of pulses in the rectifier 32. Each partial inverter 60 is electrically conductively connected on the AC voltage side to a secondary winding of the matching transformer 56, whose primary winding is electrically conductively connected to a busbar 62 in the substation 50. The filter 58 is likewise connected to this busbar 62. By way of example, the smoothing inductor 52 is arranged in a positive input line 64 to the inverter 54. The positive input line 64 and a negative input line 66 are electrically inductively connected to the positive and negative busbars 44 and 46 in the wind energy installations 4, which are electrically connected in parallel, by means of a direct-current transmission device 68. The direct-current transmission device 68 may on the one hand be two direct-current lines or one direct-current cable.
Thyristors are provided as the converter valves for the rectifiers 32 for each wind energy installation 4 and the inverter 54 in the grid-side converter station 48. The rectifiers 32 regulate a power, and the polyphase voltage is regulated by means of the inverter 54. This interconnection of n converter stations corresponds to an HVDC multipoint grid.
The publication entitled “Offen für Offshore—HVDC Light—Baustein einer nachhaltigen elektrischen Energieversorgung” [Open for Offshore HVDC Light—Module for sustainable electrical power supply] discloses an offshore wind farm in which a direct-current cable is used instead of a polyphase cable. A power converter is provided at each of the two ends of this direct-current cable, and these converters are each provided with a power transformer on the AC voltage side. IGBT converters are provided as the power converters, as known from a DC-link converter for medium voltage. The DC-link capacitor is split in two, and DC voltage connections of each IGBT converter are each electrically connected in parallel. One wind energy installation in this wind farm in each case has a generator-side IGBT converter whose grid-side IGBT converters are integrated in an IGBT converter of a grid-side converter station. The IGBT converters of the wind energy installations in this wind farm are connected on the DC voltage side by means of a direct-current cable to the IGBT converter in the grid-side converter station. This direct-current concept allows the wind energy installations in a wind farm, in particular in an offshore wind farm, to be more than 140 km away from a grid-side converter station.
The publication entitled “Control method and snubber selection for a 5MW wind turbine single active bridge DC/DC converter” by Lena Max and Torbjörn Thiringer, printed in the Conference Proceedings for EPE 2007 in Aalborg, discloses a further embodiment of a DC voltage concept for a wind farm. In this embodiment, each wind energy installation has a generator, a generator-side converter and a DC voltage converter. A plurality of wind energy installations are linked by means of a further DC voltage converter to a DC voltage converter which is connected by means of a direct-current cable to a grid-side inverter at a wind farm feed point to a regional supply grid. Either a diode rectifier or a self-commutated IGBT converter is provided as the generator-side converter for each wind energy installation.
The invention is now based on the object of improving a wind energy installation and a wind farm consisting of these wind energy installations in such a way that it is possible to save installation parts.
According to the invention, this object is achieved by the characterizing features of claim 1 and claim 8, respectively.